Adhyaya 84: शिवव्रतकथनम्
Uma–Maheshvara Vrata, Shula-dana, and Month-wise Ekabhakta Vrata
पौर्णमास्याममावास्यां वर्षमेकमतन्द्रिता उपवासरता नारी नरो ऽपि द्विजसत्तमाः
paurṇamāsyāmamāvāsyāṃ varṣamekamatandritā upavāsaratā nārī naro 'pi dvijasattamāḥ
En la luna llena y en la luna nueva, durante un año entero sin descuido, una mujer—o también un hombre, oh mejores entre los dos veces nacidos—que permanece vigilante y entregado al ayuno (upavāsa) se hace digno de la gracia que desata los lazos de pāśa del alma-paśu, mediante una observancia firme dirigida al Pati, Śiva.
Suta Goswami
It prescribes a year-long discipline of fasting on Pūrṇimā and Amāvāsyā as a purificatory vrata that supports Śiva-pūjā and ripens the devotee for Śiva’s anugraha (grace).
Śiva is implied as Pati—the liberating Lord—whose grace is approached through steadiness (atandritā) and self-restraint, weakening pāśa (bondage) that constrains the paśu (individual soul).
Upavāsa as a vrata: periodic fasting on lunar junctions (full and new moon) for a year, a tapas-oriented practice aligned with Shaiva observance and preparatory to deeper Pāśupata discipline.